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Hyaluronan promotes the chondrocyte response to BMP-7
R A Andhare1, N Takahashi, W Knudson
1Department of Biochemistry, Rush Medical College, Rush University Medical Center, Chicago, IL, USA.
Osteoarthritis and Cartilage
|February 7, 2009
Summary
Hyaluronan in the chondrocyte matrix modulates responses to bone morphogenetic protein-7 (BMP-7). Restoring CD44-hyaluronan interactions promotes cellular responsiveness to BMP-7, but not transforming growth factor-beta1 (TGF-beta1).
Area of Science:
- Cell Biology
- Biochemistry
- Biomaterials Science
Background:
- Chondrocytes respond to bone morphogenetic proteins (BMPs) and transforming growth factor-betas (TGF-betas).
- The hyaluronan receptor CD44 interacts with Smad1, a key mediator of BMP signaling.
- The pericellular matrix, rich in hyaluronan, influences chondrocyte behavior.
Purpose of the Study:
- To investigate how hyaluronan in the pericellular matrix modulates chondrocyte responses to BMP-7 and TGF-beta1.
- To determine the role of CD44-hyaluronan interactions in mediating these cellular responses.
Main Methods:
- Studied nuclear translocation of Smad1, Smad2, and Smad4 in bovine articular chondrocytes.
- Examined effects of hyaluronidase treatment (matrix disruption) and hyaluronan addition (matrix repair).
- Utilized a CD44 reporter construct to assess luciferase expression in response to BMP-7.
Main Results:
- Disrupting the hyaluronan matrix diminished Smad1 and Smad4 nuclear translocation in response to BMP-7.
- TGF-beta1-induced Smad2 and Smad4 nuclear translocation was unaffected by matrix disruption.
- Adding hyaluronan restored Smad1/Smad4 nuclear translocation and enhanced BMP-7-induced signaling, including Smad1 phosphorylation.
Conclusions:
- Hyaluronan-CD44 interactions are crucial for robust chondrocyte responses to BMP-7.
- These interactions have minimal impact on TGF-beta1 signaling pathways.
- Modulating cell-hyaluronan interactions presents a mechanism to regulate BMP-7 responsiveness in chondrocytes.
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